Abstract
Background: Botulinum toxin type A (BoNT-A) has been proposed as an adjunct to orthognathic surgery because its temporary neuromuscular effects may reduce muscular loading during postoperative healing and potentially influence fixation stability, skeletal relapse, and postoperative recovery. This systematic review aimed to evaluate the available clinical evidence regarding the adjunctive use of BoNT-A in orthognathic surgery. Methods: A systematic literature search was conducted in PubMed, the Cochrane Library, and Google Scholar in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Clinical studies directly comparing orthognathic surgery with and without adjunctive BoNT-A administration and reporting outcomes related to mechanical stability, skeletal stability, or postoperative recovery were included. Risk of bias was assessed using the Cochrane Risk of Bias 2 (RoB 2) tool for randomized controlled trials and ROBINS-I for the non-randomized study. Results: Three studies met the eligibility criteria, comprising two randomized controlled trials and one retrospective comparative study. Considerable heterogeneity was observed in surgical procedures, targeted muscles, BoNT-A doses, timing of administration, and evaluated outcomes. Individual studies reported associations between BoNT-A administration and a lower incidence of fixation plate fracture, reduced anteroposterior skeletal relapse at the Pogonion, or lower preanalgesic pain scores and postoperative opioid consumption. However, these findings were derived from different studies evaluating distinct interventions and outcomes and were not consistently demonstrated across comparable outcome measures. Conclusions: BoNT-A may represent a promising adjunct to orthognathic surgery, with potential benefits for fixation-related mechanical stability, selected parameters of skeletal relapse, and postoperative pain management. However, the limited number of studies, methodological limitations, and substantial clinical heterogeneity preclude definitive conclusions. Further well-designed randomized controlled trials with standardized injection protocols and longer follow-up are required before routine clinical use can be recommended.